1. Field of the Invention
The present invention relates generally to a wireless power receiver and a control method for the same and, more particularly, to a wireless power receiver for wirelessly receiving power based on an electromagnetic resonant technique and a control method of the same.
2. Description of the Related Art
Mobile terminals such as a mobile phone, a PDA (Personal Digital Assistant) and the like are powered by rechargeable batteries, and the battery of the mobile terminal is charged using a separate charging apparatus. In general, a separate contact terminal is arranged external to the charging apparatus and the battery, and the charging apparatus and the battery are electrically connected to each other through contact between the respective external terminals.
However, since the contact terminal outwardly protrudes in this contact type charging scheme, the contact terminal is easily contaminated by foreign substances and thus the battery charging is often not correctly performed. Further, the battery charging may also not be correctly performed when the contact terminal is exposed to moisture.
Recently, a wireless charging or a non-contact charging technology is developed and used for electronic devices to solve the above-mentioned problem.
This wireless charging technology employs wireless power transmission/reception, and corresponds to, for example, a system in which a battery can be automatically charged if the battery is laid on a charging pad without any physical connection of the mobile phone to a separate charging connector. The wireless charging technology is generally used to charge a wireless electric toothbrush or a wireless electric shaver. Accordingly, a waterproof function can be improved since electronic products are wirelessly charged through the wireless charging technology, and the portability of electronic devices can be increased since there is no need to provide a wired charging apparatus. Therefore, developments of technologies related to the wireless charging technology are expected to significantly increase, particularly with development of electric cars.
The wireless charging technology largely includes an electromagnetic induction scheme using a coil, a resonance scheme using a resonance, and an RF/microwave radiation scheme converting electrical energy to microwave energy and then transmitting the microwave energy.
The electromagnetic induction scheme is considered to be mainstream, and is expected that all electronic products will in the future be charged, anytime and anywhere, without any hard wire connection, particularly in view of the strength of recent successful experiments for wirelessly transmitting microwave power to a destination located dozens of meters away.
A power transmission method through the electromagnetic induction corresponds to a scheme of transmitting power between a first coil and a second coil. When a magnet approaches the coil, an induced current is generated. A transmission side generates a magnetic field using the induced current and a reception side generates energy through an induced current according to changes in the magnetic field. The phenomenon is referred to as magnetic induction, and the power transmission method using magnetic induction has a high energy transmission efficiency.
With respect to the resonance scheme, Prof. Soljacic of MIT announced a system in which electricity is wirelessly transferred using a power transmission principle of the resonance scheme based on a coupled mode theory, even if a device to be charged is separated from a charging device by several meters. The wireless charging system employs a physical concept based on a resonated electromagnetic waves containing electrical energy instead of resonating sound energy. The resonated electrical energy directly transfers only when there is a device having a resonance frequency and any portion of unused electrical energy is reabsorbed into an electromagnetic field instead of being spread in the air, with the electrical energy not otherwise affecting surrounding machines or people.
Meanwhile, a wireless power receiver according to the conventional resonance scheme performs a communication function with a wireless power supplier based on a predetermined mode, and transmits a charging state of the wireless power receiver, a control signal for controlling the wireless power supplier, and the like. However, the conventional wireless power receiver should have a separate communication module for communication, other than a power reception means for wirelessly receiving power from the wireless power supplier, for example, a coil. Complications arise because the wireless power receiver cannot distinguish a signal for power supply and a signal for communication, thereby requiring an additional communication module.
Accordingly, problems occur since conventional wireless power receiver have an increased total volume due to the additional communication module, and have an increased power consumption to drive the communication module.